It has been a practice, for more than a half century, to use acetylene as a fuel in this technical field. However, the physical and chemical nature of acetylene makes it very dangerous to keep it compressed in the natural state, and currently it is stored in a porous material after having been compressed and dissolved in a solvent, such as acetone. Under these conditions, the weight of acetylene stored or shipped is slight in relation to the weight of the container and its contents.
Shipping and storage of acetylene in the liquid state has been considered, but because of the risk of explosion and the difficulty in handling, pure liquified acetylene is not used.
Use of mixtures of acetylene has been proposed, thus avoiding the risks of explosion and making it possible to obtain a combustion temperature high enough to perform welding and oxygen cutting operations. On the other hand, it is known that addition of acetylene to a fuel gas can impart to the latter welding performances similar to those of acetylene. Now, although it is easy to make up gaseous mixtures having a constant composition, such is not the case when the mixture is stored in the liquid state where the gaseous phase is different, in chemical composition, from the liquid phase. In the case of an ethylene-acetylene mixture, an enrichment in acetylene content occurs, while in the case of a propylene-acetylene mixture there is an impoverishment in acetylene content, which after a certain time results in a mixture which is unsuitable for welding.
This difficulty can be avoided by removal of the liquid phase from the mixture, the content of which remains constant to the extent that the liquid is not heated at high temperatures or for long periods of time.
Generally, in industry, heating of the liquid cannot be avoided and it is necessary to relieve the excess pressure which creates a modification of the mixture content. This phenomenon is very important when insulation of the container is poor or when the cryogenic container is stored too long.
For several years an effort has been made to find combustible mixtures having a fairly constant acetylene content which do not require special equipment for its distribution as a liquid, as is the case for ethylene-acetylene mixtures.
Mixtures have been found that are distributable in liquid form using standard cyrogenic liquid equipment and the gaseous and liquid phases of which have a fairly constant acetylene content. These combustible gaseous mixtures, obtained by natural evaporation of the liquid phase, without removal of the latter, represent a saving in investment for the user because of a simplification of the equipment in relation to the use of binary ethylene-acetylene mixtures as fuels.
With known ethylene-acetylene mixtures, there is preferred evaporation of the ethylene compound and consequently the acetylene enrichment in content of the liquid phase occurs. Proposed ternary mixtures that do not exhibit acetylene enrichment in the liquid phase are less explosive and thus meet safety standards better.